The present invention relates to impact-type crushers which utilize centrifugal force to hurl rocks to be crushed against an impact surface and, more particularly, to an improved rock feeding arrangement for such crushers.
Impact-type crushers utilizing centrifugal force to hurl rocks to be crushed are generally known. For example, in U.S. Pat. No. 4,126,280, issued Nov. 21, 1978, to Burk, rock is fed into a rotating impeller which hurls the rock against a plurality of anvils disposed in a ring concentric with the access of rotation of the impeller. As another approach, U.S. Pat. No. 3,970,257, issued July 20, 1976, to McDonald et al., a rotating impeller throws the rock against a bed of crushed rock instead of the anvils.
In either case, a primary design consideration is providing for a sufficient useful life span of the apparatus, particularly those portions of the apparatus which come in contact with the rock as it is passed through the device. For example, portions of the device, such as impeller vanes and upper and lower plates within the impeller, are subject to a great deal of wear while they are accelerating the rock. As a result, any portions subject to wear require periodic replacement, which necessitates substantial down time for the equipment and incurs considerable cost for replacement of worn parts.
One portion of the apparatus which is subject to wear is the feed arrangement for directing rock to be crushed into the impeller. In a typical crusher, a hopper is mounted atop the device with a feed tube extending downwardly from the hopper passing through an opening in an impeller cover plate. Rock to be crushed travels from the hopper through the feed tube and is directed to the impeller interior, from which it is thrown against the impact surface.
Considerable wear occurs on the hopper interior as the rock moves therefrom into the feed tube. Additionally, the interior of the lower end of the feed tube is particularly subject to wear, due to rock rebounding from the impeller interior, and since the rock is moving at its greatest speed as it exits the feed tube into the impeller. More importantly, dust and small particles from the rock as it enters the impeller tends to collect between the feed tube exterior and the opening through the impeller cover plate into which the feed tube extends. This material collects to such an extent that the clearance between the feed tube and impeller cover plate is entirely filled, which does provide some advantage in that the accumulated material serves as a seal to prevent the dust and small particles from entering the region above the impeller. Nonetheless, rotation of the impeller causes the accumulated material to quickly wear away the feed tube exterior, resulting in relatively frequent replacement of the feed tube.
What is needed, therefore, is a feed tube arrangement which enables use of a single feed tube for greater periods of time before replacement is required. Such an arrangement, of course, should not interfere with overall design of the remainder of the rock crusher and, preferably, should be capable of use with existing crushers on a retrofit basis.